Field water level adjustment device

Abstract

To provide a device for adjusting water level in paddy field that has a simple structure and does not increase the labor burden on farmers, can stably maintain the paddy field water level at the agricultural management water level at all times, efficiently stores floodwaters without increasing the drainage volume even if the water level rises during heavy rain, and can reliably eliminate floodwaters with a constant drainage volume after heavy rain.SOLUTION: A device for adjusting water level in paddy field comprises a drainage pipe 1 installed at a position lower than a paddy field surface G of a paddy field 20, a sheath pipe 2 connected to the drainage pipe 1 and extending vertically upward, an overflow pipe 3 with an open top that can rise and fall while loosely inserted into the sheath pipe 2, and a float 4 and a notch 5 arranged in a line around the upper end of the overflow pipe 3, the notch 5 being an open-top rectangle cut from top to bottom, and when the overflow pipe 3 is lowered to its lowest point, the lower edge of the notch 5 being at the agricultural target water level.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to an apparatus for adjusting the field water level of a paddy field according to purposes.

Background Art

[0002] Paddy fields have come to be used not only for original rice cultivation, but also as so-called "paddy field dams" that temporarily store rainwater during heavy rainfall to reduce damage such as river flooding (Patent Documents 1 to 3).

[0003] Patent Document 1 describes a paddy field water storage amount adjusting apparatus, in which, in order to exert a paddy field dam function in a paddy field, a retaining plate insertion gate opening and a water storage amount adjusting plate insertion gate opening are provided; a retaining plate is vertically inserted into the retaining plate insertion gate opening, and a water storage amount adjusting plate is vertically inserted into the water storage amount adjusting plate insertion gate opening; water is drained from a narrow portion at a lower part of a notch to maintain a farming management water level of the paddy field, and in case of heavy rainfall, rainwater is stored up to a maximum water storage level that is obtained by adding an overflow height to a farming target water level.

[0004] Patent Document 2 describes a paddy field water level adjusting apparatus, in which, in order to exert a paddy field dam function in a paddy field, a water level adjusting plate with variable height is installed inside a basin body having a drainage hole; a dam plate that is taller than the water level adjusting plate and is provided with a water discharge hole having a smaller diameter than the drainage hole on a lower side is disposed on the basin body, and paddy field water overflowing the water level adjusting plate is stored and gradually discharged from the water discharge hole to the drainage hole side.

[0005] Patent Document 3 describes a water outlet water level regulator that is held by a water outlet basin and has a water outlet with a float-type water level regulator, stating that the conventional technologies such as Patent Documents 1 and 2 do not meet the requirements for a paddy field dam function. The water outlet with a float-type water level regulator has a downward-opening float and a downward-opening float connecting pipe, the downward-opening float has a locking projection formed at the lower end of the downward-opening float pipe, and a float restraining valve is formed at the upper end of the downward-opening float connecting pipe that engages with the locking projection to limit the vertical operating range of the downward-opening float, thereby adjusting the buoyancy of the downward-opening float and causing water to flow into the main water outlet according to the relationship between the position of the upper surface of the downward-opening float and the water level. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2012-120510 [Patent Document 2] Japanese Patent Publication No. 2017-51137 [Patent Document 3] Japanese Patent Publication No. 2022-97700 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] The water storage adjustment plate described in Patent Document 1 causes the water level to rise even with a small amount of inflow into the paddy field when the water level is near the target water level for farming, resulting in an unstable water level at all times. Furthermore, when the water level rises above a certain level, the overflow water depth increases, the amount of drainage increases, and the water storage efficiency deteriorates.

[0008] In the dam plate with discharge holes described in Patent Document 2, when the water level in the paddy field rises, the water pressure increases, the amount of water drained increases, and the water storage efficiency deteriorates. In addition, floating debris such as straw fragments easily clogs the discharge holes, and in this clogged state, the water stored in the paddy field cannot be reliably drained after a flood.

[0009] The water level regulator for the drain outlet described in Patent Document 3 also had the following problems. As shown in Figure 12 of the same document, under normal circumstances, water flows down through the gap between the float pipe and the float connecting pipe, so floating debris such as mud and straw contained in the water tends to clog this gap, making the adjustment function unstable. Also, since the amount of water drained through the gap is thought to be small, even a little rain can cause the water level on the rice paddy surface to rise quickly, making it difficult to maintain an appropriate water level for farm management.

[0010] Furthermore, as shown in Figure 13 of the same document, the upward movement of the float until water flows down from the main water outlet at the top of the float is small, and the range that can be adjusted by the float is narrow (WE2-WE1 in the same figure). As a result, the water level rises until the float is fully raised, and once it exceeds the float, it is drained all at once, making it impossible to secure a stable water level on the paddy field surface.

[0011] Furthermore, as shown in Figure 14 of the same document, the highest point of the vertical watertight plate becomes the adjusted water level (WE3 in the same figure), so the position of the vertical watertight plate needs to be adjusted. It is thought that the drainage volume is adjusted not only by the float function but also by the vertical watertight plate working together, making the structure complex. In addition, it becomes necessary to store water based on rainfall forecasts and to perform drainage operations in response to the decrease in the water level on the paddy field surface as needed. The drop water pipe connected to the float is fixed in place buried in the soil, and it is not practical for farmers to dig it up according to the farm management water level, as this would be a heavy burden of labor.

[0012] Therefore, the object of the present invention is to provide a paddy field water level adjustment device that has a simple structure and does not increase the burden of labor on farmers, can stably maintain the water level on the paddy field surface at the farming management level under normal circumstances, efficiently stores floodwaters without increasing the amount of drainage even when the water level rises during heavy rains, and reliably removes floodwaters with a constant amount of drainage after heavy rains. [Means for solving the problem]

[0013] [1] A paddy field water level adjustment device comprising a drain pipe installed at a position lower than the paddy field surface (ground), a sheath pipe communicating with the drain pipe and extending vertically upward, an overflow pipe with an upward opening that can be raised and lowered while loosely inserted into the sheath pipe, and a float and a notch arranged in the circumferential direction of the upper end of the overflow pipe, wherein the notch is an upward-opening rectangle cut out from top to bottom, and the lower edge of the notch is at the farming target water level when the overflow pipe is lowered to its lower limit.

[0014] [2] In the above [1], there are preferably multiple floats and notches, and the floats and notches are alternately provided in the circumferential direction of the upper end of the overflow pipe. This is because the buoyancy of the floats and the water falling into the overflow pipe from the notches are generated without bias in the circumferential direction of the overflow pipe, making it easier for the overflow pipe to rise and fall smoothly without tilting.

[0015] [3] In the above [1] or [2], it is preferable that a packing is attached to the outer circumference of the overflow pipe, which abuts against the upper end of the sheath pipe when the overflow pipe is lowered to its lower limit. This is because it prevents mud and floating debris from entering the gap between the overflow pipe and the sheath pipe.

[0016] [4] In any of the above [1] to [3], it is preferable to include a rise limiting member that restricts the rise limit of the overflow pipe, because this prevents the overflow pipe from coming out of the sheath pipe.

[0017] [5] In the above [4], it is preferable that the rise restricting member can change the rise limit of the overflow pipe. This is because the amount of water stored can be changed by adjusting the stroke of the overflow pipe. Furthermore, when the water level approaches the height of the levee, the rise of the overflow pipe is restricted, the water level exceeds the float height and overflows all around, the amount of drainage increases and restricts further rises in the water level, thereby preventing damage to the levee due to overflow.

[0018] [6] In any one of the above [1] to [5], it is preferable that a closing body for closing the end of the drainage pipe on the paddy field side is detachably attached to said end. This is because by removing this closing body, water is drained from said end to eliminate the paddy field water level, allowing the paddy field to be used for upland farming such as vegetable cultivation.

[0019] [7] In any one of the above [1] to [6], it is preferable that the drainage pipe, the sheath pipe, the overflow pipe, the notch and the float are housed in a drainage basin. Effects of the Invention

[0020] According to the paddy field water level adjusting device of the present invention, with a simple structure and without increasing the labor burden on farmers, it exhibits the excellent effect of being able to stably maintain the paddy field water level at the farming management water level under normal conditions, efficiently store floodwater without increasing drainage volume even if the water level rises during heavy rain, and reliably discharge floodwater at a constant drainage volume after heavy rain. Brief Description of the Drawings

[0021] [Figure 1] Fig. 1 is a partially broken perspective view showing the paddy field water level adjusting device of Embodiment 1. [Figure 2] Fig. 2 is a perspective view showing the device when installed in a paddy field and functioning as a paddy dam. [Figure 3] Fig. 3 is a cross-sectional view of Fig. 2. [Figure 4] Fig. 4 shows the paddy field water level adjusting action of the device, wherein (a) is a cross-sectional view at the target farming water level, and (b) is a cross-sectional view at the water level during small-scale rainfall drainage. [Figure 5] Fig. 5 shows said adjusting action, wherein (a) is a cross-sectional view at the water storage water level, and (b) is a cross-sectional view at the maximum water storage water level. [Figure 6] Fig. 6 shows said adjusting action, and is a cross-sectional view when there is no paddy field water level for upland farming. [Figure 7] Fig. 7 is a partial plan view showing a modified example of the overflow pipe, the float and the notch in the device. Mode for Carrying Out the Invention

[0022] 1. Drain pipes and sheath pipes The materials for the drain pipes and sheath pipes are not particularly limited, but examples include resin, clay, concrete, and metal, and rigid polyvinyl chloride pipes can be used particularly suitably. The dimensions of the drain pipe and sheath pipe are not particularly limited, but examples include those with an inner diameter of 75 to 300 mm, and those with an inner diameter of 100 to 250 mm are preferred. The drain pipe and the sheath pipe may be joined mechanically or chemically, but an L-shaped or T-shaped pipe integrally formed from rigid polyvinyl chloride can be preferably used, and a T-shaped pipe is particularly preferred when attaching the aforementioned closure body.

[0023] 2. Overflow pipe The material of the overflow pipe is not particularly limited, but examples include resin, metal, etc., and rigid polyvinyl chloride pipe can be used particularly suitably. The inner diameter of the overflow tube is preferably 1 to 3 mm larger than the outer diameter of the sheath tube, and more preferably 1 to 2 mm larger. This is to allow the overflow tube to move smoothly up and down relative to the sheath tube, while preventing water from substantially flowing through the gap between the overflow tube and the sheath tube, thereby preventing mud and floating debris from entering the gap. The upward and downward strokes of the overflow pipe are not particularly limited, but are preferably 100 mm or more in order to increase the water storage capacity, more preferably selected from the range of 100 to 500 mm, and most preferably selected from the range of 150 to 400 mm. Furthermore, it is preferable that the strokes be adjustable within a predetermined range selected from 150 to 400 mm in order to adjust the water storage capacity.

[0024] 3. Float As mentioned above, the number of floats is preferably multiple, specifically 2 to 4, and more preferably 2 to 3. The multiple floats are preferably arranged at equal pitches in the circumferential direction of the upper end of the overflow pipe. The material used for the float is not particularly limited, but examples include resin, rubber, and metal. The material for the float is not particularly limited, but examples include hollow bodies and closed-cell foams.

[0025] 4. Notch As mentioned above, the number of notches is preferably multiple, specifically 2 to 4, and more preferably 2 to 3. It is preferable that the multiple notches are provided at equal intervals in the circumferential direction of the upper end of the overflow pipe. The width of the notch is not particularly limited, but it is preferably 19 mm or more, more preferably 40 to 170 mm, and most preferably 45 to 120 mm, in order to prevent floating debris from getting caught. It is desirable to set the number of notches so that the width of the outer circumference opening of the float through which water flows when it flows toward the notch is 120 mm or more, in order to easily swallow floating debris. The total width of the (one or more) notches is not particularly limited, but is preferably 80 to 340 mm, and more preferably 100 to 230 mm, in that it allows for a moderate amount of water to be dropped without being too large. The depth of the notch is not particularly limited, but is preferably 20 mm or more, more preferably 30 to 120 mm, and most preferably 40 to 100 mm.

[0026] 5. Lifting restraint member The upward restricting member is not particularly limited, but examples include bars installed in the drainage manhole that contact the float that limits the upward movement. The rise-regulating member that can change the rise limit of the overflow pipe is not particularly limited, but examples include the aforementioned bar installed in the drainage manhole so as to be able to change its installation height. [Examples]

[0027] Next, embodiments of the present invention will be described with reference to the drawings. Note that the structure, materials, shape, and dimensions of each part of the embodiments are illustrative and can be modified as appropriate without departing from the spirit of the invention.

[0028] The paddy field water level W adjustment device in the embodiment shown in Figures 1 to 6 is installed at the boundary between the paddy field 20 and the embankment 21 surrounding the paddy field 20, with a waterway 22 adjacent to the embankment 21. The paddy field water level adjustment device is A drainage pipe 1 is installed at a lower position than the surface G of the paddy field 20, A sheath pipe 2 that is connected to the drain pipe 1 and extends vertically upward, An overflow pipe 3 with an upward opening that can be raised and lowered with a maximum stroke of 200 mm while loosely inserted into the sheath pipe 2, Two floats 4 and two notches 5 are alternately provided in the circumferential direction at the upper end of the overflow pipe 3, The drainage manhole 6 containing these, A drainage channel 7 guides the water that flows from drainage pipe 1 to drainage manhole 6 into waterway 22. It includes and is composed of.

[0029] In the drain pipe 1 and sheath pipe 2, rigid polyvinyl chloride T-shaped pipes with an inner diameter of 131 mm and an outer diameter of 140 mm (JIS standard VU125) are used, with the straight section of the pipe extending horizontally as drain pipe 1 and the branched section extending upward as sheath pipe 2. The underside of drain pipe 1 is located approximately 300 mm below the paddy field surface G. A closing body 8 is detachably attached to the paddy field side end of the drainage pipe 1, for example, by a screw structure, to close the end. The waterway-side end of drain pipe 1 is connected to the waterway-side wall of drain manhole 6, opening outside the manhole, and to which drain channel 7 is connected.

[0030] The overflow pipe 3 is made of rigid polyvinyl chloride pipe with an inner diameter of 125 mm and an outer diameter of 130 mm (non-standard LP125). Because the outer diameter of the overflow pipe 3 is 1 mm smaller than the inner diameter of the sheath pipe 2, the overflow pipe 3 can move up and down relative to the sheath pipe 2, but water does not flow through the gap between the overflow pipe 3 and the sheath pipe 2.

[0031] Each float 4 is a hollow resin body with an outer height of 70 mm, forming a fan shape with a central angle of 120° (circumference of the inner side of 136 mm) in a plan view, and is attached to the outer circumference of the upper end of the overflow pipe 3. It is designed to have buoyancy that can lift the overflow pipe 3.

[0032] Each notch 5 is formed by cutting out the upper end of the overflow pipe 3 between the floats 4 from the upper edge downwards, maintaining a central angle of 60° in plan view (circumference on the inner side is 68 mm, resulting in a width of 63 mm), to a depth of 70 mm (the same as the outer height of the float 4 in this example). The total width of the two notches 5 is 126 mm (Figure 7(d)). The lower edge of notch 5 is set to be at the farming target water level when the overflow pipe 3 has descended to its lower limit (Figure 4(a)), and the lower edge of notch 5 functions as the overflow lower edge.

[0033] The two floats 4 are provided at equal intervals (180° at the central angle) around the upper end of the overflow pipe 3, and the two notches 5 are also provided at equal intervals. As described above, the overflow pipe 3 can easily rise and fall smoothly without tilting.

[0034] A pin serving as a downward restricting member 9 is inserted into the side of the overflow pipe 3. When the overflow pipe 3 descends to its lower limit, the downward restricting member 9 (via the packing 10 in this example) comes into contact with the upper end of the sheath pipe 2, thereby restricting the downward limit of the overflow pipe 3.

[0035] An elastic rubber O-ring packing 10 is attached to the outer circumference of the overflow pipe 3. When the overflow pipe 3 is lowered to its lower limit, the packing 10 comes into contact with the upper end of the sheath pipe 2, sealing the gap between the overflow pipe 3 and the sheath pipe 2 and preventing mud and floating debris from entering the gap.

[0036] The drainage basin 6 is formed in a box shape using concrete or the like, with an open top and a side facing the paddy field. A retaining plate 11 is attached to the side facing the paddy field to retain the soil beneath the paddy field surface G.

[0037] A bar is installed in the drain basin 6 as a rise restricting member 12 that restricts the upper limit of the overflow pipe 3, and the rise restricting member 12 can change the upper limit of the overflow pipe 3. Specifically, multiple pairs of engagement holes 13 at different height levels are formed on the upper part of the opposing surface of the drain basin 6, and when the rise restricting member 12 is installed by inserting both ends into predetermined engagement holes 13, the upper surface of the float 4 comes into contact with the rise restricting member 12 when the overflow pipe 3 rises from the lower limit by a predetermined stroke, thereby restricting the upper limit.

[0038] Furthermore, a pair of locking holes 14 are formed at the midpoint height of the opposing surfaces of the drainage basin 6. When the rising restricting member 12 is installed by inserting both ends into the locking holes 14, the upper surface of the float 4 comes into contact with the rising restricting member 12 when the overflow pipe 3 is at the lower limit, thereby restricting the overflow pipe 3 from rising. Thus, this restriction can also be used to prevent the paddy field from being used as a paddy field dam.

[0039] The paddy field water level W adjustment device configured as described above provides the following effects. (a) composition The paddy field water level W adjustment device of this embodiment has a simple and basic structure and does not use electricity or other power sources, so it can be easily and inexpensively installed in paddy fields. Furthermore, since the adjustment of the water level in the paddy field is performed automatically by buoyancy, as described below, the labor burden on farmers does not increase.

[0040] (i) at all times As shown in Figure 4(a), the normal water level W in the paddy field is the "target water level for farming," the overflow pipe 3 of the paddy field water level W adjustment device is at its lower limit, and the lower edge of the overflow of the notch 5 is at the target water level for farming. As shown in Figure 4(b), even under normal conditions, if there is an excess of water supplied to the paddy field or during light rainfall, the water level W on the paddy field surface rises slightly. At this time, the buoyancy generated on the float 4 is small, and the overflow pipe 3 does not rise. Therefore, the water slightly exceeds the lower edge of the overflow of the notch 5 and flows into the overflow pipe 3 like a continuous flow, and is gradually drained into the waterway 22 via the drain pipe 1 and drainage channel 7. Thus, the water level W on the paddy field surface can be maintained at the "water level during light rainfall drainage" (a farming management water level that is acceptablely higher than the aforementioned farming target water level). Furthermore, as mentioned above, since the water is drained through the notch 5, which has sufficient width, it is highly unlikely that debris will clog the notch 5, and even if it does clog, it can be easily removed manually.

[0041] (c) During heavy rain As shown in Figure 5(a), during heavy rainfall, the water level W on the paddy field surface clearly rises. At this time, as the water overflows the lower edge of the notch 5 and falls into the overflow pipe 3, a large buoyancy is generated on the float 4, causing the overflow pipe 3 to rise. If the rain stops, the rise of the overflow pipe 3 stagnates, and the water level W on the paddy field surface maintains the "storage water level" for a while. However, if the heavy rain continues, as shown in Figures 2 and 3, the overflow pipe 3 will rise until the upper surface of the float 4 contacts the rising restricting member 12 (rising limit). As shown in Figure 5(b), if the heavy rain continues, the water level W on the paddy field will rise further, and not only will water fall from the notch 5, but the water will also overflow the top of the float 4 and fall into the overflow pipe 3. The water will then be drained into the waterway 22 via the drain pipe 1 and the drainage channel 7, so the water level W on the paddy field will reach the "water level when stored" and will be maintained at that level. In this way, by storing water in the rice paddies, the paddies can function as dams, reducing risks such as overflow from the levees, flooding in the waterway 22, and ultimately, river flooding. The overflow pipe 3 has a large stroke of up to 200 mm, allowing it to exert a large flood storage capacity.

[0042] (e) After the heavy rain After the heavy rain ends, water flows from the lower edge of the overflow of notch 5 into the overflow pipe 3. However, since the total width of the multiple notches 5 is 126 mm, the amount of water that flows out remains moderate and constant. As a result, the amount of water drained into the waterway 22 via the drain pipe 1 and drainage channel 7 also remains moderate and constant, and the water level W on the paddy field steadily decreases over a long period of time. In this way, even after the heavy rain ends, the water on the paddy field can be safely drained without the risk of downstream damage.

[0043] (O) When planting fields As shown in Figure 6, by removing the closing body 8 attached to the paddy field end of the drain pipe 1, the paddy water can be drained from that end, and the paddy field can be used for field crops such as vegetables. At this time, if the rise restricting member 12 is installed with both ends inserted into the locking holes 14, the overflow pipe 3 will not rise.

[0044] Next, Figure 7 is a plan view of a modified example in which the dimensions of the overflow pipe 3, float 4, and notch 5 have been changed, with the width of notch 5 and the total width indicated. (a) to (c) use an overflow pipe 3 with an inner diameter of 75 mm and an outer diameter of 80 mm (non-standard SU75), with (a) being an example with two notches 5 with a central angle of 60°, (b) being an example with three notches 5 with a central angle of 40°, and (c) being an example with four notches 5 with a central angle of 30°. (d) to (f) use the LP125 rigid polyvinyl chloride pipe for the overflow pipe 3, (d) is the above embodiment (an example in which two notches 5 with a central angle of 60° are provided), (e) is an example in which three notches 5 with a central angle of 40° are provided, and (f) is an example in which four notches 5 with a central angle of 30° are provided. (g) to (i) use a rigid polyvinyl chloride pipe with an inner diameter of 202 mm and an outer diameter of 216 mm (JIS VU200) for the overflow pipe 3. (g) is an example in which two notches 5 with a central angle of 60° are provided, (h) is an example in which three notches 5 with a central angle of 40° are provided, and (i) is an example in which four notches 5 with a central angle of 30° are provided. (j) to (l) use a rigid polyvinyl chloride pipe with an inner diameter of 298 mm and an outer diameter of 318 mm (JIS VU300) for the overflow pipe 3. (j) is an example with two notches 5 with a central angle of 60°, (k) is an example with three notches 5 with a central angle of 40°, and (l) is an example with four notches 5 with a central angle of 30°.

[0045] It should be noted that the present invention is not limited to the embodiments described above, and can be appropriately modified and implemented without departing from the spirit of the invention. [Explanation of symbols]

[0046] 1 Drain pipe 2 sheath tube 3 Overflow pipe 4 floats 5 notches 6. Drainage manhole 7 Drainage channel 8 Closed body 9. Lowering restraint member 10 packing 11 Retaining board 12. Lifting restraint member 13 Engagement holes 14 Locking holes 20 rice paddies 21 ridge 22 waterways G Tamen W Rice field water level

Claims

1. A paddy field water level adjustment device comprising: a drain pipe (1) installed at a position lower than the surface of the paddy field; a sheath pipe (2) communicating with the drain pipe (1) and extending vertically upward; an upward-opening overflow pipe (3) that is loosely inserted into the sheath pipe (2) and can move up and down; and a float (4) and a notch (5) arranged in the circumferential direction of the upper end of the overflow pipe (3), wherein the notch (5) is an upward-opening rectangle cut out from top to bottom, and the lower edge of the notch (5) is at the farming target water level when the overflow pipe (3) is lowered to its lower limit.

2. The paddy field water level adjustment device according to claim 1, wherein there are multiple floats (4) and notches (5), and the floats (4) and notches (5) are alternately provided in the circumferential direction of the upper end of the overflow pipe (3).

3. The paddy field water level adjustment device according to claim 1, wherein a packing (10) is attached to the outer circumference of the overflow pipe (3) and contacts the upper end of the sheath pipe (2) when the overflow pipe (3) is lowered to its lower limit.

4. The paddy field water level adjustment device according to claim 1, comprising a rise restricting member (12) that restricts the rise limit of the overflow pipe (3).

5. The paddy field water level adjustment device according to claim 4, wherein the rising regulating member (12) can change the rising limit of the overflow pipe (3).

6. The paddy field water level adjustment device according to claim 1, wherein a closing body (8) for closing the end of the drain pipe (1) on the paddy field side is detachably attached.

7. A paddy field water level adjustment device according to any one of claims 1 to 6, wherein the drain pipe (1), sheath pipe (2), overflow pipe (3), notch (5), and float (4) are housed in a drain basin (6).

Images